Conventional wireless communication systems typically include a network consisting of a plurality of network devices, and a plurality of base transceiver stations (BTS) to allow the network to communicate with a plurality of mobile communication units (MU) by way of a wireless medium. Typically, in such conventional wireless communication systems, a mobile communication unit (MU) may be communicating with a base transceiver station (BTS) in various media access control (MAC) states. In CDMA2000-based wireless communication systems, for example, such MAC states include dormant, active, and control/hold state. These states are explained in more detail below with reference to the following example.
FIG. 1A illustrates a block diagram of an exemplary conventional wireless communication system 100. The conventional wireless communication system 100 consists of a network 102 and a plurality of base transceiver stations (BTS) 104, 106, and 108 coupled to the network 102. The base transceiver stations (BTS) 104, 106, and 108 are assigned to communicate with a plurality of mobile communication units (MU), one of which is shown in this example as mobile communication unit 110 assigned to communicate with base transceiver station (BTS) 106. It shall be understood that base transceiver station (BTS) 106 may communicate with other mobile communication units (MU) (not shown) in addition to mobile communication unit (MU 110). Also, the other base transceiver stations (BTS) 104 and 108 may communicate with other mobile communication units (MU) (not shown).
FIG. 1B illustrates a diagram of various media access control (MAC) states in which the mobile communication unit (MU) 110 communicates with the base transceiver station (BTS) 106 in the conventional wireless communication system 100. As discussed above, the three MAC states are the dormant, active, and control/hold. In the dormant state, the mobile communication unit (MU) 110 maintains only common channels with the base transceiver station (BTS). The common channels are used by all the mobile communication units (MU) assigned to communicate with the base transceiver station (BTS). In the dormant state, the mobile communication unit (MU) 110 does not have a dedicated channel to communicate with the base transceiver station (BTS) 106. The mobile communication unit (MU) 110 uses the common channels to obtain one or more dedicated channels for transmitting and receiving data to and from the base transceiver station (BTS) 106.
When the mobile communication unit (MU) 110 has received an assignment of a dedicated channel and begins to send and/or receive data to and from the base transceiver station (BTS) 106, the mobile communication unit (MU) 110 is in the active state. In the active state, the mobile communication unit (MU) 110 has a dedicated control channel (DCCH) if the data rate is 9.6 kbps plus a dedicated traffic channel (i.e., the supplemental channel (SCH)) for higher data rates to communicate with the base transceiver station (BTS) 106. More specifically, the mobile communication unit (MU) 110 communicates control and power messages as well as data (e.g., voice and/or non-speech data) by way of the dedicated control channel (DCCH). If the data rate between the mobile communication unit (MU) 110 and the base transceiver station (BTS) 106 is above 9.6 kbps, then the mobile communication unit (MU) 110 also uses the supplemental channel (SCH) to transmit and receive data to and from the base transceiver station (BTS) 106. The mobile communication unit (MU) 110 remains in the active state as long as data is being transmitted; or if it has ceased, until a predetermined time period thereafter.
If the predetermined time period of no data transmission has expired while the mobile communication unit (MU) 110 is in the active state, the mobile communication unit (MU) 110 enters the control/hold state. In the control/hold state, the mobile communication unit (MU) 110 has a dedicated channel (e.g., a dedicated control channel (DCCH) or a fundamental channel (FCH)) with the base transceiver station (BTS) 106, but not a supplemental channel (SCH). As discussed above, the mobile communication unit (MU) 110 communicates control and other signaling messages as well as data to the base station transceiver (BTS) 106 by way of the dedicated channel. The mobile communication unit (MU) 110 returns to the dormant state from the control/hold state if it is does not send or receive data in the control/hold state for a predetermined time period.
FIG. 1C illustrates a diagram of a conventional Walsh code assignment scheme for mobile communication units (MU) in the control/hold MAC state. While in the control/hold state, the base transceiver station (BTS) 106 assigns a Walsh code to the mobile communication unit (MU) 110 for use as a dedicated channel. In fact, when there are a plurality of mobile communication units (MU) in the control/hold state, the base transceiver station (BTS) 106 assigns one Walsh code per each mobile communication unit (MU). In CDMA2000, the base transceiver station (BTS) 106 uses 64 Walsh codes to communicate with its assigned mobile communication units (MU). Some of those Walsh codes are reserved for common channel applications, such as for the pilot, paging, and synchronization channels. Thus, there may be, for example, only 39 remaining Walsh codes for use by respective mobile communication units (MU) in the control/hold state for respective dedicated channels. Accordingly, the number of mobile communication units (MU) that can be supported in the control/hold state is limited to a relatively low number (e.g., 39).